A kinetic study of the early steps in the oxidation of chlorophenols by hydrogen peroxide catalyzed by a water-soluble iron(iii) porphyrin

Abstract

The kinetics and mechanism of the initial steps in the oxidation of 2,4,6-trichlorophenol by hydrogen peroxide using iron(III) meso-tetra(4-sulfonatophenyl)porphine chloride as a catalyst were studied in this work. The first oxidation step is the formation of a substituted 1,4-benzoquinone. This step was also studied using a selection of differently substituted chlorophenols. It was shown that the rate constants characteristic for the oxidation of the substrate do not follow the pattern of pK_as, but correlate well with the ¹³C chemical shifts of the carbon atoms directly bonded to the oxygen in chlorophenols. The kinetics of the catalyzed and uncatalyzed oxidation of 2,6-dichloro-1,4-benzoquinone by hydrogen peroxide was also studied. The catalyzed and uncatalyzed pathways give different products.